Pledges made by Tony Blair to force housebuilders to improve the energy efficiency of homes to cut Britain's greenhouse gas emissions are to be ditched, the Guardian has learned.

Proposed building regulations due to be announced this week have been watered down and some provisions dropped altogether as "unnecessary gold plating".

When the prime minister introduced the government's energy white paper in 2003 he promised that new building regulations, to be brought in during 2005, would be 25% tougher than the ones produced in 2002. New regulations for older, refurbished homes were also to be introduced at the end of this year. His aim was to bring Britain closer to the standards of the rest of northern Europe.

But last week, only days after the end of the G8 summit when Mr Blair vowed to continue international efforts on greenhouse gas emissions, Yvette Cooper, the housing minister, decided to drop regulations on refurbished houses altogether and postpone regulations for new buildings until next year.

The decision has caused tension between the Department of Environment and the Office of the Deputy Prime Minister. The environment minister, Elliott Morley, after repeated requests, is due to see Ms Cooper tomorrow.

Mr Blair is expected to chair the cabinet committee on energy on Thursday, a day before the new building regulations are due to be announced to the House of Commons.

Ms Cooper wants to drop plans for energy efficiency improvements in existing homes which have an extension or are to be reburbished. It had been intended that from January 1 next year homeowners or builders would have to spend an extra 10% of any building project on cost-effective energy efficiency measures like roof insulation. The regulation required the householder to do this to reduce the "carbon footprint" of their home.

This was part of the Department of Environment's climate change strategy to reduce emissions and was expected to save 500,000 tonnes of carbon dioxide by 2010 to help the government meet its 20% CO 2 reduction target. It had been widely welcomed by consumer groups.

The Guardian understands that Ms Cooper decided to ditch this regulation, describing it as "unnecessary gold plating" to civil servants.

Last week Mr Morley was asked in the House of Commons about the building regulations for new buildings and said that they would come into force in April 2006. He also said that the regulations would improve energy efficiency by 20%-30%.

But information obtained by the Guardian shows that the new instructions for builders designed by civil servants will actually only deliver around 18% better results than the existing regulations, and then only if they are properly policed. The lower target figure is as a result of lower standards on cavity wall insulation, one of the key energy saving areas.

Currently local authorities do not have either the staff or the equipment to police building regulations. The Building Research Establishment at Garston, Watford, has shown that 60% of new homes do not conform to existing building regulations.

Last Friday Lady Perry, who chaired a House of Lords inquiry on energy efficiency, said the government "simply does not have a coherent policy on energy efficiency".

Andrew Warren, chairman of the Association for the Conservation of Energy, said: "The ODPM seems intent on undermining the whole government strategy for climate change and is sending the wrong signal to the building industry and householders. They seem to have a completely seperate policy than the rest of government."

Mr Blair seems certain to raise the issue at a cabinet committee meeting on Thursday when a possible review of government policy on nuclear power stations is also on the agenda. One of the reasons civil servants are keen for an official review of the option of building new nuclear stations is that they say energy efficiency measures are not working.

An ODPM spokesman said announcements on the building regulations would be made "in due course".